1. Field of the Invention
This invention relates to an electrolytic copper plating bath and to an electroplating method that uses it. More particularly, it relates to the electrolytic copper plating bath that may be applied with advantage to a circuit board where blind via holes and through holes exist together, and the method for electroplating using the electrolytic copper plating bath.
2. Description of Related Art
As the electronic components are becoming smaller in size, an increasing demand has been raised towards elevating their integration degree. To meet such demand, the packaging method is transitioning from peripheral terminal or area terminal packaging towards three-dimensional packaging. For this reason, attempts are being made to provide for current conduction to or connection of a semiconductor chip or an interposer by a through-electrode. As in the copper damocene process or in via filling for a printed circuit board, a need is felt for filling a blind via hole with a copper plating film by electrolytic copper plating.
On the other hand, a printed circuit board having both a through hole and a blind via hole has come into use. With the through hole, a copper plating film is formed on the inner wall surface of the hole and, with the blind via hole, copper plating is introduced into the inside of the hole by way of via-filling. It has thus become necessary to effect via-filing and plating of a through hole simultaneously.
However, in case the plating bath of the related technique, aimed at via-filling, is used for through hole plating, the film thickness at the through hole corner becomes unusually thin, thus possibly causing the corner crack. The plating bath of the related technique may thus not be usable for through hole plating. On the other hand, with the plating bath aimed at through hole plating, such as that proposed in the technique shown in Patent Publication 1, the film thickness at the inner bottom of the blind via hole becomes thin, such that it is difficult to fill the blind via hole with a copper plating precipitate. Hence, a need is felt for a plating bath with which the blind via hole and the through hole may be plated simultaneously.